When my washing machine empties there is a glug, glug sound in the kitchen sink. The septic tank was checked two days ago and is fine for another year. There is a clean out pipe between the house and the septic tank and it is clear. I don't see a vent pipe in the roof from the utility room. There is a pipe in the wall behind the washer that is capped off. Should this pipe be vented through the roof instead of being capped off and would it take care of the glug? Thanks, Elaine